Techno Interview

ExceptionHandling

COURSES

04 Month
DURATION

01 Hours

Define different type of Exception and its example?

Checked Exception	Unchecked Exception
Checked Exception directly inherit the property of throwable class	Unchecked Exception inherit the Runtime Exception
Occurs at Compile time	Occurs generally on run time
throws can handle checked exception	throws can handle both
Sql exception , io exception and class notfound exception are part of checked exception	arrayIndex OuterbondException, arithmetic exception and null pointer exception are example of it.

Difference between Error and Exception?

Error	Exception
Error occurs due to lack of system resource	Exception occurs due to code in program
Error generally occurs on runtime	Exception generally occurs on compile and runtime
Once the error occurred program will terminated	Program will not terminated if we handle it will follow
Outof MemoryError Virtual machineError NoClass DefError	NullPointer Exception Array IndexOuter BondException classNot foundException

Difference between ClassNotFound Exception and NoClassDefine Error?

ClassNotFound Exception	NoClassDefine Error
ClassNotFound exception occurred when path of exception is not executed correctly	NoClassDefine error occurred when class definition was present at compile time but missed at run time.

what is Try, Catch and Finally block in Exception Handling in java?

Try: try block is used to defined the exception ,it is definition block which must include with catch and finally .only try block will not executed ,either catch or finally block must be present in the code along with try block.

Catch: catch block is used to handled the exception .it must be included with try block and followed by finally block. for handling multiple exceptions, we may have multiple catch block.

Try without catch block is possible but catch without try is not possible.
When multiple catch block is used then unchecked exception will be handled first and then exception class other wise unreachable catch lock exception occurred.

Finally: finally block is structure of block which execute to check whether exception is handled properly or not.it is independent of the execution of try and catch block. Try without catch but with finally will be possible.

Finally, will not execute only in two situations:

When system crashed.
When system. exit () method is called.

Difference between final, finally and finalize keyword in java?

Final	Finally	Finalize
Final is a keyword	Finally is block	Finalize is a method
Final restricts the access of class, method and variable	Finally will execute in exception handling to check whether exception is handled properly or not	Finalize is used for garbage collection
Final when used with class that cannot be extended further	Finally will not executed when system crashed or system. exit() method called	It will execute after system.gc() method called.
Final when used with method, that cannot be overridden
When used with variable that cannot be reinitialized.

Difference between Throw and Throws in Java?

Throw()	Throws()
Throw is followed by instance	Throws is followed by class
Throw is not used to handle checked exception	Throws is used to handle checked exception
Throw is used to call exception explicitly	Throws defined the exception
Throw is present inside method	Throws are present in method signature
Throw handle only one exception at a time	Throws can handle more than one exception at a same time

How to create custom Exception in java?

When we extend exception class then custom checked exception is created whereas when runtime exception class is extended hen custom unchecked exception is created.

Create custom exception :

import java.util.Scanner;
          class IlligalException extends Exception {
              public IlligalException(String s) {
                  super(s);
              }
          }
          public class CustomException {
              public static void validate(int age) throws IlligalException {
                  if (age < 20) {
                      throw new IlligalException("Age is below 19");
                  } else {
                      throw new IlligalException("please ignore");
                  }
              }
              public static void main(String[] args) {
                  Scanner sc = new Scanner(System.in);
                  System.out.println("Enter the age");
                  int age = sc.nextInt();
                  try {
                      validate(age);
                  } catch (Exception e) {
                      System.out.println(e);
                  }
              }
          }

What happen if exception throws by main method ?

When exception I thrown by main () method it will terminate the program at runtime and print exception method at console. If file not founded filenotfoundexception thrown.

ExceptionHandling

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DURATION